The Pilot Stroke Data Bank project has developed operational diagnostic algorithms for the classification of stroke type. These algorithms are based on the type of laboratory evidence available (CT, angiography, etc.), its findings, and the severity of stroke as measured by the neurologic exam. In this study, the usefulness of these diagnostic algorithms in differentiating etiology and predicting outcome is evaluated. The use of the algorithms as a supplement to the more traditional diagnoses is also explored, as well as correlations between diagnosis and various factors relating to initial stroke severity, subsequent neurological deficit, stroke recurrence, and mortality. Plans for data analyses have been formulated.